Port 3110: sim-control — A Name Without a Story

What Port 3110 Is

Port 3110 sits in the registered ports range (1024–49151). These ports are neither the well-known system ports (0–1023) — the ones like HTTP's 80 or SSH's 22 that require root privileges to open — nor the ephemeral ports (49152–65535) that operating systems hand out dynamically to outgoing connections. The registered range is the middle ground: ports that applications can request from IANA, named and catalogued, theoretically reserved.

IANA lists port 3110 as assigned to sim-control — "simulator control port" — registered over both TCP and UDP by someone named Ian Bell.¹ That's the entirety of the public record.

The Ghost in the Registry

No RFC defines what sim-control does. No widely deployed software is publicly documented as using port 3110. No community exists around it. Search for "sim-control port 3110" and you'll find port reference databases copying each other's single-line entries, all tracing back to the same IANA assignment.

This isn't unusual. The registered ports range contains thousands of assignments made over decades, many registered by individuals or small companies for internal software that never saw broad adoption, was never publicly documented, or was simply abandoned. The IANA registry captures the moment of registration, not the lifetime of a protocol.

Port 3110 is a legitimate assignment. It just isn't a living one.

What You Might Actually See on Port 3110

Because port 3110 has no dominant real-world owner, you're more likely to encounter it used opportunistically:

• Malware and scanners sometimes use obscure registered ports to blend into traffic that looks "named" rather than random
• Custom internal applications occasionally pick ports in this range by hand, without registering them
• Gaming engines and simulation software may use nearby ports in the 3000–3200 range for local control traffic

If you see unexpected traffic on port 3110, treat it as you would any unrecognized port — find out what's listening before assuming it's benign.

How to Check What Is Listening on Port 3110

macOS / Linux:

# Show process listening on port 3110 (TCP)
sudo lsof -i TCP:3110

# Or with ss (Linux)
sudo ss -tlnp sport = :3110

Windows:

netstat -ano | findstr :3110

Take the PID from the output and look it up:

# macOS / Linux
ps aux | grep <PID>

# Windows
tasklist | findstr <PID>

If nothing is listening, that's normal. Port 3110 has no software pushing it into everyday use.

Why Unassigned-in-Practice Ports Matter

The registered ports range exists to prevent collisions — two applications claiming the same port on the same machine causes problems. The system works when everyone registers and everyone checks. It works less well when registration happens once, documentation never follows, and software evolves around the registry rather than with it.

Port 3110 illustrates the gap. It has a bureaucratic identity. It doesn't have a real one.

That gap is where confusion lives. And it's why, when you find something unexpected on a port with a name but no story, you look closer rather than assuming the name explains it.